The present invention relates generally to punch assemblies such as those usable with indexable multiple station turret punch machines.
It is known to provide rotatable and indexable punching tools in a turret punch press where the upper and lower punching tools are rotated synchronously for different orientations of the punch tools. Further, it is known to provide multiple station turret punch machines which provide a large number of different punch stations for use in conjunction with a like number of opposing die surfaces. Each station may include an upper punch assembly and a lower die assembly. The typical configuration of the punch assembly includes a punch tip that is mounted onto the lower end of a punch driver which, in turn, is threadably connected to a punch head.
As illustrated in U.S. Pat. No. 4,375,774, which is incorporated herein by reference, the punch tip can become dull or worn during use. As a result, the tips are routinely sharpened using a grinding operation which shortens the overall length of the punch tip, and accordingly, the overall length of the punch assembly. Because the distance between the cutting edge of the punch tip and the workpiece is a critical dimension, control of the vertical position, and hence the overall length of the punch assembly, is important. U.S. Pat. No. 4,375,774 discloses an adjustable punch assembly whereby the punch driver is threadably attached to the punch head. By rotating the punch driver with respect to the punch head, the overall length of the punch assembly can be shortened or lengthened.
Further, punch presses having indexable tool stations enable the punch assembly, and hence the punch tip, to be rotated so that the punch tip can be applied to the workpiece in different orientations. Punch presses employing indexable punch stations are disclosed in U.S. Pat. Nos. 5,048,385 and 4,658,688, both of which are incorporated herein by reference and both of which are owned by the assignee of the present application.
Specifically, U.S. Pat. No. 4,658,688 discloses a turret punch press having an upper and lower turret tool holder which carries a number of punch and die sets in individual tool holding stations in the turrets. At least one of the corresponding tool holding stations in the upper and lower turrets is indexable to different angular orientations. Rotation of the indexable punch tools is accomplished by a slidably mounted motor for engagement with a timing pulley, which, through a timing belt and harmonic gear drive, acts to rotate the tool holder which carries the punch and die set. In this device, each of the turrets may be equipped with tool stations which receive tool support devices that are rotatable to selectively position the tools at chosen angular positions by rotating the tool sets about their longitudinal axes.
U.S. Pat. No. 5,048,385 discloses a punch assembly for an indexable punching station which includes a striker body having a solid portion and a punch carrier which carries a plurality of individual punches. A selectively actuable stop holds the striker body stationary, allowing the punch holder to be rotated so that one of the plurality of punches will underlie the solid portion of the striker body. The stop may then be deactivated so that the entire punch assembly may be rotated to a variety of angular orientations. Rotation of the assembly thus permits a single punch to be used to punch holes of the same shape but with differing angular orientations.
Thus, U.S. Pat. No. 4,375,774 discloses an adjustable punch assembly whereby the overall length of the punch assembly may be adjusted to accommodate for wear on the punch tip or the shortening of the punch tip due to sharpening or grinding operations. U.S. Pat. Nos. 4,658,688 discloses an indexable tool station which permits the angular rotation of the punching tool. U.S. Pat. No. 5,048,385 expands on this concept by enabling the angular rotation of the entire punch assembly and further angular rotation of a tool holder to thereby selectively dispose a selected punch tool under the solid portion of the striker body.
However, the punch tip disclosed in U.S. Pat. No. 4,658,688 and punch tips generally known in the art are attached to the punch driver by a threaded shaft that passes through axial passageways in both the punch head and the punch driver. The shaft needs to be tightened to a specific torque rating in order to properly retain the punch tip. Thus, changing the punch tip in favor of an alternative punch tip is time consuming and therefore costly. Accordingly, there is a need in the punch press art for punch tips that may be changed more quickly and therefore more economically than currently available punch tips.
Further, while U.S. Pat. No. 4,658,688 discloses a punch assembly having an overall length that may be adjusted by rotating the punch head with respect to the punch driver, the design disclosed in U.S. Pat. No. 4,658,688 requires that any length adjustment be made during the initial installation of the punch tip. There is no way to adjust the overall length of the punch assembly during operation of the punch press. Accordingly, there is a need for an improved punch assembly that may be length adjusted during operation to compensate for tip wear, changes in the workpiece material or other operational variables.
The present invention satisfies the aforenoted needs by providing an improved punch assembly and an improved punch press.
The punch assembly of the present invention includes a punch driver with an axial passageway extending therethrough. The axial passageway of the punch driver accommodates a locking shaft that is releasably coupled to the punch tip. More specifically, the locking shaft includes a downwardly directed tapered socket for receiving an upper end of a punch tip shaft that extends upward from the punch tip. The upper end of the punch tip shaft includes one or more detents that form one half of a ball/detent connection between the punch tip and the punch driver.
The axial passageway extending through the punch driver includes a lower end that accommodates a cylinder which receives the punch tip shaft. The cylinder includes a plurality of spaced holes, each hole being in alignment with a ball that is trapped between an inside surface of the socket and a cylinder.
To connect the punch tip to the locking shaft that extends through the punch driver, the locking shaft, and specifically the socket, is pushed downward onto the upper end of the punch tip shaft. As a result, an inside surface of the socket pushes the balls through the spaced holes of the cylinder so that the balls engage the detent disposed at the end of the punch tip shaft to provide a ball/detent connection between the punch tip shaft and the locking shaft.
In an embodiment, the locking shaft further comprises an upper end that is spring biased upwards and a middle section disposed between the upper end of the locking shaft and the socket, which is disposed at the lower end of the locking shaft. This middle section comprises a slot having a lower portion and an upper portion. The punch driver further comprises a cooperating key that is accommodated in the slot. As the locking shaft is pushed downward, and the key is disposed in the upper portion of the slot, the balls are pushed inward through the base openings of the cylinder by the inside surface of the socket so that the balls engage the detent of the punch tip shaft to make the ball/detent connection.
In an embodiment, an upper portion of the slot disposed in the middle section of the locking shaft extends horizontally and the lower portion of the slot extends vertically so that in order to lock the socket of the locking shaft onto the upper end of the punch tip shaft, the locking shaft is pushed downward so that the key of the punch driver extends through the vertical portion of the slot and then the locking shaft is twisted thereby causing the key to travel along the horizontal portion of the slot to lock the socket over the upper end of the punch tip shaft.
In an embodiment, the punch assembly further comprises a punch head that is threadably connected to an upper end of the punch driver. The punch head also includes an axial passageway that is in alignment with the axial passageway disposed in the punch driver. As a result, the upper end of the locking shaft is accessible through the axial passageway of the punch head.
In an embodiment, the punch driver is further equipped with a downwardly biased ejector pin that engages an upper surface of the punch tip and that assists in the removal of the punch tip from the punch driver.
In an embodiment, to remove the punch tip from the punch assembly, the locking shaft is rotated until the key of the punch driver is in alignment with the vertical portion of the slot disposed in the middle section of the locking shaft. When the key is in alignment with the vertical portion of the slot, the spring biasing of the locking shaft upward in combination with the spring biasing of the ejector pins downward, causes the upper end of the punch tip shaft to be pushed downward to release the ball/detent connection between the punch tip shaft and the socket of the locking shaft.
In an embodiment, a lower end of the axial passageway passing through the punch driver accommodates a ring structure. The ring structure, in turn, accommodates and supports the cylinder and prevents upward movement of the cylinder relative to the lower end of the axial passageway when the punch tip shaft is inserted upward through the cylinder to make the ball/detent connection.
In an embodiment, the punch assembly further comprises a punch head that is threadably connected to an upper end of the punch driver. The punch head is substantially disposed within a collar; the punch driver is substantially disposed within a punch guide. The collar includes an outwardly extending upper flange and is further axially disposed within a spring. The spring is trapped between the upper flange of the collar and the punch guide. The collar also includes a plurality of spaced openings disposed below the upper flange. The upper end of the punch head further comprises a plurality of outwardly and radially extending fingers that extend through the openings of the collar to engage an upper end of the spring. Upon depression of the punch head in a downward direction, the fingers engage the spring to compress the spring downward.
In an embodiment, the fingers are an integral part of a ring structure disposed on top of the punch head.
In an embodiment, the ring structure is disposed between an upper end of the punch head and an upper punch cap.
In an embodiment, the punch cap includes a notch for engaging a striker or brake mechanism that prevents rotational movement of the punch cap and punch head upon rotation of the punch driver. In this way, the lower portion of the punch assembly, i.e. the punch driver and punch tip, may be rotated with respect to the punch head to axially lengthen or axially shorten the punch head assembly.
In an embodiment, the axial length of the punch head assembly is adjusted by rotating the punch guide, which results in a rotation of the punch driver and punch tip, while, at the same time, the punch head is held in place.
The present invention also provides an improved punch press apparatus comprising a punch assembly which includes a punch driver accommodated within a punch guide for axial movement within the punch guide. The punch guide prevents rotational movement of the punch driver with respect to the punch guide. The punch assembly further comprises a punch head threadably attached to an upper portion of the punch driver and a punch tip connected to a lower end of the punch driver. Rotation of the punch driver with respect to the punch head results in an axial lengthening or an axial shortening of the punch assembly. The punch head further includes a notch for engaging a lock means which prevents rotational movement of the punch head upon rotation of the punch guide and punch driver. The punch press apparatus further includes a linkage for transmitting rotational movement from a motor to the punch guide and punch driver to thereby lengthen or shorten the punch assembly.
In an embodiment, the punch press apparatus of the present invention further includes a means for sensing the overall length of the punch assembly.
In an embodiment, the means for sensing the overall length of the punch assembly comprises a sensor for detecting a relative vertical position of a target disposed on the punch assembly. The sensor is linked to a controller for activating or deactivating the motor.
In an embodiment, the target sensed by the means for sensing the overall length of the punch assembly is disposed on the punch head.
In an embodiment, the target which is sensed by the means for sensing the overall length of the punch assembly is disposed on the punch tip.
In an embodiment, the means for sensing the overall length of the punch tip assembly comprises a proximity switch and a target.
In an embodiment, the means for sensing the overall length of the punch tip assembly comprises an acoustical transmitter and a receiver, the receiver detecting the presence of the punch assembly between the transmitter and the receiver.
In an embodiment, the means for sensing the overall length of the punch assembly comprises a light transmitter and a receiver, the receiver detecting the presence of the punch assembly between the transmitter and the receiver.
In an embodiment, the punch press apparatus of the present invention further comprises a punch cap mounted onto an upper end of the punch head. The notch for engaging the lock means is disposed on the punch cap.
It is therefore an advantage of the present invention to provide an improved punch assembly with an improved connection between the punch tip and the punch driver to facilitate the removal and installation of the punch tip onto the punch driver.
Another advantage of the present invention is an improved method of measuring the overall length of the punch assembly and adjusting the overall length of the punch assembly.
Another advantage of the present invention is to provide an improved means of engaging the spring with the punch head during the compression of the punch assembly.
Another advantage of the present invention is to provide an improved means of ejecting a punch tip during the removal of the punch tip from the punch driver.
Another advantage of the present invention is to provide an improved means of controlling and adjusting the overall length of a punch head assembly.
Other advantages and objects of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.